1. Field of the Invention
The present invention relates to an electrode structure of a piezoelectric vibrator for a portable telephone or a portable information terminal.
2. Description of related art
As a piezoelectric vibrator of a related art, there is provided a structure in which, for example, upper and lower faces of a vibrator comprising a piezoelectric vibrator piece and an upper portion of a frame integrally formed at a base end portion of the piezoelectric vibrator piece, are provided with a lid and a base having recess portions having spaces to a degree of not hampering vibration of the piezoelectric vibrator piece.
When a plurality of respective members of piezoelectric vibrators as describe above are formed on a wafer having a large area and mass-produced by a unit of the wafer, according to an electrode pattern such as an excitation electrode film formed on an individual vibration piece, in order to grasp electric properties by individually exciting the vibration piece, it is necessary to arrange independently each of electrode patterns.
According to such a structure, when there is adopted a method of a method of bonding the respective members under high temperature and applying voltage by interposing a bond film as in anode bonding, by feeding electricity respectively to a plurality of the electrode patterns provided to a face of the wafer opposed to a side of a lid formed with a plurality of the vibrators, electricity is fed to the bond film of the wafer formed with the base and the vibrators and the bases are bonded earlier. Successively, extension electrodes to outer electrodes are formed at the wafer formed with the bases, electricity is fed to the respective extension electrodes, electricity is fed to the bond films on the side of the lids and the lids and vibrators are bonded.
However, according to the above-described method, when the lids and the bases are formed at a wafer having a material with thermal expansion different from that of the wafer formed with the vibrators, at a time point of bonding the wafer formed with the vibrators and the bases, by a difference in the thermal expansion coefficient of the wafer formed with the vibrators and the bases, warp is caused and therefore, a large area thereof enlarging a warp amount can not be bonded.
In view of the foregoing drawbacks in the conventional art, it is an object of the invention to provide a piezoelectric vibrator having an electrode structure which prevents the occurrence of warp in a bonding operation and which is capable of bonding a large area with high productivity.
According to an aspect of the invention resolving the above-described problem, when there is fabricated, in a unit of wafer, a piezoelectric vibrator having a structure including a pair of a lid and a base having recess portions having spaces to a degree of not hampering vibration of a piezoelectric vibrator piece on upper and lower faces of an vibrator comprising the piezoelectric vibrator piece and a frame-like portion integrally connected to a base end portion of the piezoelectric vibrator piece and surrounding the piezoelectric vibrator piece, there is provided an electrode structure of the piezoelectric vibrator characterized in that a plurality of the vibrators each comprising the piezoelectric vibrator piece and the frame-like portion are formed on the wafer, a plurality of electrode patterns each comprising a pair of excitation electrodes formed on the piezoelectric vibrator piece and bond films on the frame-like portion connected to the excitation electrodes and respectively formed independently from each other, are added with sputter films for shortcircuiting capable of being bonded to lids for shortcircuiting respectives thereof and the plurality of electrode patterns are connected to each other. By forming the sputter films for shortcircuiting and connecting all of the respective electrode patterns, electricity can be supplied simultaneusly to the bond films on two faces of the substrate. Thereby, according to the invention, three sheets of wafers can be bonded simultaneously, occurrence of warp after bonding can be prevented and a large area can be bonded.